1. Field of the Invention
The present invention relates to toner and a toner manufacturing method.
2. Description of Related Art
Techniques for decreasing power consumption of an electrophotographic printing system image forming apparatus, represented by a copier, a printer, and the like, have been examined in recent years under consideration for environment. As an example of the techniques, the technique of using a toner having a controlled melting property by using a polyester resin as a base material is disclosed.
For example, Japanese Patent Application Laid-Open Publication No. 2000-47430 discloses a toner aiming at coping with both of low-temperature fixability and offset resistance by including a hybrid resin component having a vinyl series copolymer unit and a polyester unit as binder resins.
Furthermore, Japanese Patent Application Laid-Open Publication No. 2009-58927 discloses a technique for keeping the elastic modulus and the fixation ratio of a toner by cross-linking the polyester including a trivalent carboxylic acid with a functional group capable of reacting with a carboxyl group.
Furthermore, Japanese Patent Application Laid-Open Publication No. 2005-173578 discloses a technique for reacting a polyester resin and a compound having an active hydrogen group by a cross-linking reaction. To put it concretely, the technique is the one for reacting an isocyanate modified polyester with a diamine compound by urea cross-linking.
Although the toners manufactured by the techniques described above have excellent low-temperature fixability, the toners easily generate a high-temperature offset because their viscosity at a high temperature falls. Furthermore, because the toners have a high cross-linking point density, formed by a functional group having a high polarity and a high moisture adsorbing rate, the changes of the amounts of water of the toners owing to the humidity has been large. Consequently, the toners have the remaining problem in which the humidity dependency of charging becomes excessive and the deterioration of image quality caused by the humidity cannot fully be corrected by the changes of development conditions.
Furthermore, the cases of performing the saddle stitching bookbinding and the Z fold bookbinding of images having high pixel rates have increased owing to the recent progress of the post-processing equipment of image forming apparatus. Consequently, it has been required to perform the improvement for the problem in which toner exfoliates from folds of an image even when low-temperature fixing can be performed on a smooth sheet. Japanese Patent Application Laid-Open Publication No. 2009-109717 discloses an improving technique of the fold fixability, but it is not yet sufficient.